Important events in the pathogenesis of atherosclerosis are associated with the loss of the integrity of the vascular endothelium. Endothelium is unique in that its function is dependent on the continuity of a monolayer of highly differentiated cells growing on a collagenous surface which is continuously exposed to the strains of flow and pulsations. Bovine aortic endothelial cells are grown on collagen incorporated into stretchable highly hydrated hydroxyethylmethacylate/methacylate copolymers ("hydrogels"). We will evaluate the ability of aortic-, skin-, basement membrane- and other collagens to support endothelial cell adhesion, migration and replication, first under stationery conditions, then under the influence of controlled strains from flowing medium and from stretching and pulsations of the hydrogel substream. Direct microcinematographic observation and quantitative assessment of cell adhesion and migration will be correlated with transmission - and scanning electron microscopy, incorporation of H-thymidine into DNA, and specific well-focused and biochemical analysis of the collagen metabolism; hydroxylation of proline, lysine incorporation, and synthesis of collagenase digestible protein. The goal of the study is the elucidation of the principal dynamic mechanisms involved in the maintenance of the functional and morphological integrity of vascular endothelium, under the influence of strains from flow and from pulsations.